2-way soft opening valve arrangement for a shock absorber

ABSTRACT

Valve arrangement for a shock absorber is described, comprising a valve housing ( 2 ) having a first ( 7 ) and a second port ( 8 ), a pilot chamber ( 3 ) being in fluid communication with the first ( 7 ) and/or second port ( 8 ), wherein a pilot pressure (Pp) is defined by a hydraulic pressure in the pilot chamber ( 3 ). The arrangement further comprises a main valve member ( 4 ) being axially movably arranged in the valve housing ( 2 ) and being arranged to interact with a main valve seat member ( 9 ) in order to restrict a main fluid flow between the first ( 7 ) and second ports ( 8 ) in response to the pilot pressure (Pp) acting on the main valve member ( 4 ). Moreover, the main valve seat member ( 9 ) is movable between a first compression stroke position and a second rebound stroke position so that, during the compression stroke, the main fluid flow is restricted at a first restriction (R 1 ) and a cooperating serially arranged second restriction (R 2 ), and during the rebound stroke, the main fluid flow is restricted at a third restriction (R 3 ) and a cooperating serially arranged fourth restriction (R 4 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to International Application No.PCT/EP2017/053894, filed Feb. 21, 2017 and titled “2-WAY SOFT OPENINGVALVE ARRANGEMENT FOR A SHOCK ABSORBERS” which in turn claims priorityfrom European Application having serial number 16156682.3, filed Feb.22, 2016 and titled “SOFT OPENING 2-WAY VALVE ARRANGEMENT FOR A SHOCKABSORBER” both of which are incorporated herein by reference in theirentireties.

TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to the field of valvearrangements. In particular, the present invention relates to a valvearrangement for controlling a flow of damping medium in a shockabsorber.

TECHNICAL BACKGROUND

Generally, within the technical field of shock absorbers that include apilot valve, a pressure regulator, i.e. a valve arrangement, is used tocontrol a flow of damping medium between a compression chamber and arebound chamber during a reciprocal motion of a piston in a dampingmedium filled chamber of the shock absorber. The piston, via a pistonrod, is connected either to a wheel or a chassis, whereas the chamber isconnected to one of the wheel or chassis that the piston is notconnected to. During a compression stroke the piston moves axially in adirection towards the compression chamber and thereby pressurizes thedamping medium in the compression chamber. During a rebound stroke, thepiston moves axially towards the rebound chamber, i.e. in the oppositedirection, and thereby pressurizes the damping medium in the reboundchamber. In accordance with the function of the shock absorber, thepressurized damping medium needs to be transferred from the pressurizedchamber to the other chamber, i.e. from the compression chamber to therebound chamber or vice versa. The flow of damping medium needs to becontrolled to obtain a damping effect of the piston and thus the shockabsorber, i.e. to damp relative motion between the wheel and chassis.

The control of the pressure in the flow of damping medium in the shockabsorber depends on the pressure created by the pilot control valve.Pressure regulators in shock absorbers are usually provided with anaxially movable or deflectable valve member, such as a washer, cone,poppet or shim that acts against a seat part. The pressure control isachieved by equilibrium or balance of forces, for example equilibriumbetween a pressure and/or flow force acting on the valve member in onedirection and counteracting or opposing forces, such as one or more of aspring force, friction force or pilot pressure force acting on the valvemember in the opposite direction. When the piston of the shock absorbermoves at a certain speed such that the pressure and/or flow force becomegreater than the opposing or counteracting forces, the movable valvemember is forced away from the seat part, thereby opening a flowpassage. Thus, the movable valve member is forced to open at a strokedefined as a function of the flow produced by the pressure acting on theregulating area of the pressure regulator.

Traditional valve arrangements of the pressure regulating type describedabove generally have the disadvantage that when a threshold value ofpressure is reached, the valve member is opened and the flow of dampingmedium between the compression chamber and the rebound chamberdramatically increases in a distinct way. This gives a dampingcharacteristic which is not as smooth as desired. Instead, such adamping has a sharp opening with a corner that acts to dynamics thatcommonly causes instabilities such as an initial overshot and followingoscillations.

State of the art valve arrangements for shock absorbers, such as the oneshown in EP0942195B1, have a valve construction that allows a softopening, providing the desired damping characteristics. However,although this solution provides a soft opening in one flow direction,the damping flow in the opposite direction is not at all desirable.Thus, this solution works well in a 1-way valve, but it does not providethe desired damping characteristics in a 2-way valve.

Therefore, there is a need for a 2-way valve arrangement for use inshock absorbers having improved damping characteristics.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved 2-way valvearrangement providing improved damping characteristics which aresmoother than prior art.

The invention is based on the inventors' insight that in order for a2-way valve arrangement to have soft opening characteristics the valvearrangement needs restricting interfaces that are different incompression stroke compared to rebound stroke. This realization has alsolead to the surprising effect that the area ratio between thecompression pressure area and the rebound pressure may be set withoutthe prerequisite that the sum of the two areas equals the pilot pressurearea. With other words, the compression pressure area may be increasedwithout decreasing the rebound pressure area, and vice versa. This is anadvantage since the damping characteristics may be even furtherimproved.

Further, the inventor has realized that it is possible to obtain a softopening also in the rebound stroke, by providing two cooperatingserially arranged restrictions in the rebound flow.

Above-mentioned objects are realized through a valve arrangement for ashock absorber, the valve arrangement comprising a valve housingcomprising a first and a second port, a pilot chamber being in fluidcommunication with the first and/or second port, wherein a pilotpressure is defined by a hydraulic pressure in the pilot chamber. Thearrangement further comprises a main valve member being axially movablyarranged in the valve housing and being arranged to interact with a mainvalve seat member in order to restrict a main fluid flow between thefirst and second ports in response to the pilot pressure acting on themain valve member. Moreover, the main valve seat member is movablebetween a first compression stroke position and a second rebound strokeposition so that, during the compression stroke, the main fluid flow isrestricted at a first restriction and a cooperating serially arrangedsecond restriction, and during the rebound stroke, the main fluid flowis restricted at a third restriction and a cooperating serially arrangedfourth restriction.

Hereby, a valve arrangement is provided which has a soft opening duringthe compression stroke, enabled by the two cooperating radial displacedrestrictions being fluidly coupled and serially arranged, and has a softopening during the rebound stroke, enabled by the third and fourthcooperating radial displaced restrictions being fluidly coupled andserially arranged. Thus, by letting the rebound flow going throughdifferent path than the two cooperating first and second restrictionsused in the compression stroke, the soft opening may be achieved duringthe compression stroke. Further, the third and fourth restrictionsachieves a soft opening in a rebound stroke. If the rebound flow wouldgo through the same restrictions as in the compression, but in theopposite direction, the damping character would not fulfill the desiredrequirements.

Moreover, in this solution the area ratio between the compression areaand the rebound area may be adjusted without changing the pilot pressurearea. In a solution where the main valve seat is fixed, the sum of thecompression pressured area and rebound pressured area is always equal tothe pilot pressured area. However, with a movable main valve member, itis possible that said sum is greater than the pilot pressured area.Hereby, the valve arrangement may be formed to generate the desireddamping forces in both the compression stroke and the rebound strokewithout compromising with one of the forces.

In the context of this application, any restrictions “cooperating”should be understood as that they are in some way dependent on eachother and work together. E.g. the orifices of two cooperatingrestrictions may be dependent on the same parameter, such as the strokelength. Further, in the context of this application, e.g. tworestrictions being “serially arranged” or “arranged in series” should beunderstood as that the one restriction is provided upstream of the otherrestriction. That is, fluid will first go through one restriction andthen the other restriction, i.e. the fluid is not restricted in twoparallel restrictions.

In one embodiment, the first restriction is arranged upstream relativethe second restriction, in view of the compression fluid flow direction.Further, the first restriction has a smaller orifice than the secondrestriction's orifice in at least an initial stroke and when being atleast partly opened. Thereby, the fluid is first restricted by the firstrestriction and subsequently restricted by the second restriction, whichcontributes to the desired soft opening character of the damper duringthe compression stroke. Hereby, when the first and second restrictionsare at least partly open and in the initial stroke, the firstrestriction is always smaller than the second restriction, which alsocontributes to the desired soft opening character of the damper duringthe compression stroke.

In yet one embodiment, the first and second restrictions are at leastpartly formed as circumferential restrictions. In one embodiment thefirst restriction is arranged radially inwards relative the secondrestriction. Hereby, when the restrictions are radially displaced andcircumferentially formed, the orifice of the first restriction willalways be smaller than the orifice of the second restriction when beingat least partly opened.

In yet one embodiment, the third restriction is arranged upstreamrelative the fourth restriction, in view of the rebound fluid flowdirection, and wherein the third restriction has a smaller orifice thanthe fourth restriction's orifice in at least an initial stroke and whenbeing at least partly opened. Thereby, the fluid is first restricted bythe third restriction and subsequently restricted by the fourthrestriction, which contributes to the desired soft opening character ofthe damper during the rebound stroke. Further, when the third and fourthrestrictions are at least partly open in an initial stroke, the thirdrestriction is smaller than the fourth restriction, which alsocontributes to the desired soft opening character of the damper duringthe rebound stroke.

In yet one embodiment, the valve arrangement comprises a fifthrestriction being arranged in series with the second restriction. In oneembodiment the fifth restriction is arranged in parallel with the firstrestriction. In one embodiment the fifth restriction is arrangedadjacent to the first restriction. All of these embodiments may ofcourse be combined.

In one embodiment, the fifth restriction has a constant orifice beingindependent of the axial position of the main valve member relative thevalve housing. Hereby, a fifth restriction having a set orifice at alltimes is achieved. Thus, the fifth restriction's orifice is strokeindependent. In one embodiment the fifth restriction is arrangedadjacent to the first restriction, so that when the first restriction isat least partly open the first and fifth restrictions act as a commonrestriction. Hereby, the total orifice of the first and fifthrestriction may be larger than the restriction orifice of the secondrestriction in the beginning of a stroke, but smaller than the secondrestriction orifice in a larger stroke. Hereby, the total restrictingcharacter in the compression stroke may be controlled so as tocontribute to the desired soft opening character of the damper in thecompression stroke.

In yet one embodiment, the valve arrangement comprises a sixthrestriction being arranged in series with the fourth restriction. In oneembodiment the sixth restriction is arranged in parallel with the thirdrestriction. In one embodiment the sixth restriction is arrangedadjacent to the third restriction. All of these embodiments may ofcourse be combined.

In one embodiment, the sixth restriction has a constant orifice beingindependent of the axial position of the main valve member relative thevalve housing. Hereby, a sixth restriction having a set orifice at alltimes is achieved. Thus, the sixth restriction's orifice is strokeindependent. In one embodiment the sixth restriction is arrangedadjacent to the third restriction, so that when the third restriction isat least partly open the third and sixth restrictions act as a commonrestriction. Hereby, the total orifice of the third and sixthrestriction may be larger than the restriction orifice of the fourthrestriction in the beginning of a stroke, but smaller than the secondrestriction orifice in a larger stroke. Hereby, the total restrictingcharacter in the compression stroke may be controlled so as tocontribute to the desired soft opening character of the damper in therebound stroke.

In yet one embodiment, the main valve member further comprises ageometrically defined circumferential aperture having a radial innerwall and a radial outer wall, wherein the radial inner wall forms a partof the fourth restriction and the radial outer wall forms a part of thethird restriction. Hereby, the two cooperating restrictions may beachieved by the form of the main valve member, and thereby alsoachieving their cooperation since they may be moved together by movingthe axial position of the main valve member relative the seat valvemember.

In yet one embodiment, the sixth restriction is at least one openinginto said circumferential aperture in said main valve member. Hereby, arebound flow may be achieved in a simple manner which may be strokeindependent.

In yet one embodiment, the valve arrangement further comprises ageometrically defined circumferential blocking means for blocking atleast a part of the circumferential orifice of the third restriction, sothat the third restriction has a smaller orifice than the fourthrestriction's orifice in at least an initial stroke and when being atleast partly opened. An initial stroke shall be interpreted as when thestroke is larger than zero, but not the entire stroke length. The thirdrestriction may have a smaller orifice than the fourth restriction'sorifice throughout the stroke length. However, for the soft opening, itis only the initial stroke length that contributes to the desireddamping effect. Therefore, the third restriction may have a largerorifice than the fourth restriction's orifice in larger strokes.

In one embodiment the blocking means if formed so that the third orificeincreases more than linearly relative the stroke.

In one embodiment this is achieved by blocking portions that decrease insize as the distance from the base of the valve seat member increase. Inone embodiment corresponding intermediate openings increase in size asthe distance from the base of the valve seat member increase. Hereby,the blocking means may block the most damping fluid in the lower partsof the stroke, and allow an increased flow as the strokes increase.Thus, the orifice of the third restriction will increase more thanlinearly relative the stroke length.

In yet one embodiment, the third and fourth restrictions are at leastpartly formed as circumferential restrictions. In one embodiment thefourth restriction is arranged radially inwards relative the thirdrestriction. Hereby, when the restrictions are radially displaced andcircumferentially formed, the orifice of the third restriction may beblocked by the blocking means so that it will be smaller than theorifice of the fourth restriction when being at least partly opened,despite being placed radially outwards relative the fourth restriction.

In one embodiment the blocking means may be e.g. a projection or a wall.

In yet one embodiment, the blocking means is an axially extending wallblocking an envelope outer surface of the radial outer wall of said mainvalve member forming a part of the third restriction.

In yet one embodiment, the blocking means forms an integral part of thevalve seat member. Hereby, the blocking part may be achieved with fewercomponents than if it would be a separate unit.

In yet one embodiment, the blocking means constitute a separate blockingmember. In yet one embodiment, the blocking member is held in abutmentto the valve seat member by means of a biasing member. Hereby, theblocking member may be hold in place and avoid to move in anuncontrolled manner.

In yet one embodiment the movable main valve seat member is a washer ora shim. Hereby, it is possible to provide the movable valve seat memberat a low cost. In the embodiment where the movable valve seat member isa washer it may have a thickness of about 0.5-1.0 mm, preferably about0.7 mm. In the embodiment where the movable valve seat member is a shimit may have a thickness of about 0.1-0.49 mm, preferably about 0.3 mm.

In one embodiment the moveable main valve seat member is a shim. In oneembodiment, said shim has a flexibility allowing its radially outwardend to bend at pressures above a predefined threshold during thecompression stroke, so as to allow a flow of the damping medium withoutmoving the main valve member.

An advantage with having a shim being the movable valve member, is thatduring the compression stroke, the movable valve member's radiallyoutwards end may bend when high pressure pulses of pressure are exertedon the movable valve member, so as to allow a passage of damping mediumthrough the second restriction, without having to move the main valvemember. Hereby, short and intense pressure increases may be handledwithout having to move the main valve member. This further increases thesmoothness of the damping character.

In one embodiment, the moveable main valve seat member is a shim whichis tensioned against the valve housing so that the shims outer end is atleast slightly bent, when the first and second restrictions are closed.Hereby, when the movable valve member is flexible any irregularities inthe movable valve member may be compensated for through flexibility.Thus, the tolerance range may be increased during production.

In one embodiment the movable valve seat member is a washer or shimclosing an upper portion of the circumferential aperture during therebound stroke. Hereby, the movable valve seat member may prevent anymain fluid from flowing past the first and second restrictions.

In yet one embodiment the movable valve seat member is a washer or shimcomprising at least three radial steering projections meshing with themain valve housing. Hereby, the washer/shim may be designed to mesh withthe housing but to prevent non-axial movements of the movable main valvemember. The washer/shim comprises three steering projections so as torestrict the movements of the washer to substantially axial movements.Also, rotational movements around its center axis are permitted. Hereby,any “drawer behavior” may be reduced, i.e. the washer may be preventedto be tilted and locked relative the housing, and thereby it is axiallymovable at all times.

In yet one embodiment the space between the at least three radialsteering projections in the washer/shim form ports for allowing the mainfluid flow during the compression stroke.

In one embodiment, the steering projections and intermediate ports arearranged so that a straight line through any of the projection and thecenter of the washer will also go through an intermediate port. Hereby,jamming is prevented if the washer/shim is tilted (i.e. rotated aroundan axis being perpendicular to its center axis) since there are no twodirectly opposite projections along the diameter of the washer.

In yet one embodiment, the blocking means comprise a plurality ofblocking portions and intermediate openings. E.g. the blocking means maycomprise 2-10 blocking portions and intermediate openings.

In yet one embodiment, the orifices of said first restriction, secondrestriction, third restriction and/or fourth restriction is controlledby means of the axial position of the main valve member relative thevalve housing. Hereby, the restrictions may be controlled in a commonway, making them cooperatively controllable by a single control source.

In one embodiment, the movable main valve seat member is a passivemember and its axial position is controlled by the fluid pressure and/orthe position of the main valve member.

In yet one embodiment, the first restriction and the second restrictionis closed when the main valve seat member is in the rebound strokeposition. Hereby, the first and second restrictions do not affect therebound flow, but the third and fourth restriction restrict the reboundflow.

In one embodiment, the third and fourth restrictions are closed when themain valve seat member is in the compression stroke position. Hereby,the third and fourth restrictions do not affect the compression flow,instead only the first and second restrictions restrict the compressionflow.

In one embodiment the main valve seat member is always arranged tightlyagainst either the main valve member, against the housing or sandwichedbetween the main valve member and the housing. Hereby, either the firstand second restrictions and/or the third restriction are/is closed atdifferent flows.

In one embodiment the main valve seat member is always arranged tightlyagainst the main valve member during compression stroke.

In one embodiment the main valve seat member is always arranged tightlyagainst the housing during the rebound stroke.

In one embodiment, during compression stroke, when the pressure from thefirst port is below a threshold pressure value, the main valve seatmember is sandwiched between the main valve member and the housing.Further, in compression stroke, when the pressure from the first port isabove a threshold pressure value, the main valve seat member is arrangedtightly against the main valve member, but lifted from the valvehousing. Finally, during the rebound stroke the main valve seat memberis arranged tightly against the housing regardless of the pressure levelfrom the second port.

In yet one embodiment, the orifices of the first restriction, secondrestriction and/or third restriction are controlled by means of theaxial position of the main valve member relative the valve housing.

Hereby, the restrictions may be controlled by controlling the axialposition of the main valve member. This may be achieved by e.g.combination forces generated from a pilot pressure, an actuator such asa solenoid and/or spring arrangements.

In yet one embodiment the main fluid flow is restricted by the openingbetween the movable main valve seat member and the main valve memberduring a rebound stroke, and the main fluid flow is restricted by theopening between the movable main valve seat member and the main valvehousing during the compressions stroke.

In yet one embodiment at least one of the valve housing and the movablemain valve seat member further comprises a geometrically definedcircumferential aperture having a radial inner wall and a radial outerwall, wherein the radial inner wall forms a part of the firstrestriction and the radial outer wall forms a part of the secondrestriction.

Hereby, the radial inner and outer wall constitutes the two cooperatingrestrictions achieving the soft opening in the compression stroke. Inone embodiment the circumferential aperture is formed in the valvehousing and the movable valve seat member is sized and adapted tocooperate with the radial inner wall and radial outer wall of thecircumferential aperture to form the first restriction and secondrestriction, so as to restrict the main fluid flow during thecompression stroke.

Hereby, the movable valve seat member may be a simple member, such asfor example a washer. Thereby, the cost for producing the movable valveseat member may be kept low. Further, since the valve housing alreadyhas a rather complex form, it will be formed in a cutting operatingmachine such as e.g. a turning lathe or a milling cutter or similar, andthen forming the additional circumferential aperture will not be ascostly as making the aperture in the movable valve seat member. Thus anoverall cheaper solution may be provided.

In yet one embodiment the valve arrangement further comprise a controlvalve member being movable in an axial direction relative the main valvemember in response to an actuating force acting on the control valvemember, the control valve member being resiliently loaded in an oppositedirection to the actuating force by means of a biasing member, andwherein an interface between the control valve member and the main valvemember comprises an opening restricting an bleed flow of the dampingmedium between the first and second port.

In the context of this application, the bleed flow is to be understoodas a flow of damping medium being parallel to the main fluid flow.Further, the bleed flow is substantially lower flow than the maximummain fluid flow.

Hereby, the arrangement may allow a controlled variable bleed flow,which may be a first stage flow of damping medium. In a compressionstroke, the flow of damping medium from the first to the second portwill substantially go from, in the first stage, being only the bleedflow to mainly be flow through the first and second restrictioncontrolled by the main valve member in a second stage. Hereby, a softopening between the first and second stage is further improved.

In yet one embodiment, the size of the opening restricting the bleedflow in the interface between the control valve member and the mainvalve member is controlled by means of the axial position of the controlvalve member relative the main valve member.

In one embodiment, the main valve seat member comprises a first liftingsurface area arranged to hold the main valve seat member in abutment tothe main valve member in response to a hydraulic pressure in the firstport.

In yet one embodiment, the main valve seat member comprises a secondlifting surface area arranged to hold the main valve seat member inabutment to the main valve housing in response to a hydraulic pressurein the second port.

Further, in one embodiment the main valve member comprises a firstlifting surface area arranged to axially move the main valve memberrelative the valve housing in response to a hydraulic pressure in thefirst port.

In one embodiment the main valve member comprises a second liftingsurface area arranged to axially separate the main valve member from themain valve seat member in response to a hydraulic pressure in the secondport.

In one embodiment, the control valve member is arranged at leastpartially within the main valve member. In yet one embodiment, theactuating force acting on the control valve member is generated by asolenoid.

In one embodiment, the pilot pressure is regulated by a pressureregulator integrated in the control valve member.

In one aspect of the invention a shock absorbing device for a vehiclesuspension is achieved. The device comprises at least one workingchamber and a valve arrangement according to any of the aboveembodiments, for controlling the flow of a damping medium fluid to/fromsaid at least one working chamber to control the damping characteristicsof said shock absorbing device. Hereby, the valve arrangement may beincorporated in a shock absorbing device for a vehicle.

In one embodiment the shock absorbing device comprises a first workingchamber being fluidly connected to the first port of the valvearrangement and a second working chamber being fluidly connected to thesecond port of the valve arrangement 1.

BRIEF DESCRIPTION OF THE DRAWINGS

Further details and aspect of the present invention will become apparentfrom the following detailed description with reference to accompanyingdrawings, in which:

FIG. 1a shows an exploded view of an embodiment of the valvearrangement,

FIG. 1b shows an exploded view of an embodiment of the valvearrangement,

FIG. 2a shows a cross-section of an embodiment when the main valvemember is in a closed position to block a main flow from the first portto the second port,

FIG. 2b shows a cross-section of an embodiment when the main valvemember is in a closed position to block a main flow from the first portto the second port,

FIG. 3a shows a close-up cross-section of FIG. 2a , where the main valvemember is in a closed position to block a main flow from the first portto the second port,

FIG. 3b shows a close-up cross-section of FIG. 2b , where the main valvemember is in a closed position to block a main flow from the first portto the second port,

FIG. 4a is a close-up of the device in FIG. 3a , but where the mainvalve member and main valve seat member is in a partly open position toallow a regulated main flow from the first port to the second port, i.e.a flow during compression stroke,

FIG. 4b is a close-up of the device in FIG. 3b , but where the mainvalve member and main valve seat member is in a partly open position toallow a regulated main flow from the first port to the second port, i.e.a flow during compression stroke,

FIG. 5a is a close-up of the device in FIG. 3a , but where the mainvalve member is in a partly open position to allow a regulated main flowfrom the second port to the first port, i.e. a flow during reboundstroke,

FIGS. 5b and 5c are two close-ups of the device in FIG. 3b , but wherethe main valve member is in a partly open position to allow a regulatedmain flow from the second port to the first port, i.e. a flow duringrebound stroke,

FIG. 6a shows a cross-section of a side portion of the main valve seatmember in one embodiment, where the lifting surface area during theclosed position of the main valve member is illustrated,

FIG. 6b shows a cross-section of a side portion of the main valve seatmember where the lifting surface area during regulated compressionstroke is illustrated,

FIG. 6c shows an illustration of the main valve seat member and thefirst, second and fifth orifices at a given stroke length S,

FIG. 6d shows a graph over the orifice openings vs. the stroke length,

FIG. 6e shows a graph over the flow (q) vs. Pressure (P) in threedamping characteristics scenarios,

FIG. 7a shows two illustrations of the main valve seat member whenhaving an integrated blocking means,

FIG. 7b shows an illustration of the main valve seat member and theblocking means when the blocking means is a separate unit,

FIG. 7c shows an illustration of the third, fourth and sixth orifices ata given stroke length S,

FIG. 7d shows a top view of the main valve seat member in oneembodiment, and

FIG. 8 shows a side cross-sectional illustration of a shock absorberhaving a valve arrangement placed therein.

DETAILED DESCRIPTION OF EMBODIMENTS

The present invention will now be described more fully hereinafter withreference to the accompanying drawings, in which currently preferredembodiments of the invention are shown. This invention may, however, beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided for thoroughness and completeness, and fully convey the scopeof the invention to the skilled addressee. Like reference charactersrefer to like elements throughout the application. However, the mainvalve seat member 9 is denoted with either valve seat member 9, 9 a, 9 bor 9 c. The alternative versions (9 a, 9 b, 9 c) may be substituted foreach other in the different embodiments described below. Therefore, anyreference made to either one of 9, 9 a, 9 b or 9 c should be interpretedas a disclosure for all alternative embodiments of the valve seatmember. Sometimes only “9” is used as a reference in order to facilitatethe reading of the text.

The inventive concept will be described with two major embodiments, thefirst one shown in FIGS. 1a, 2a, 3a, 4a, 5a, and 7a where the moveablevalve member 9 has an integrated blocking means comprising blockingportions 91 and intermediate openings 92 for regulating the orifice ofthe third restriction R3. In the other major embodiment, shown in e.g.FIGS. 1b, 2b, 3b, 4b, 5b, and 7b the blocking means 10 is a separateunit which comprise blocking portions 91 and intermediate openings 92,having the same function as the blocking portions and intermediateopenings in the first embodiment. The two embodiments still have thesame function and are merely two ways of solving the same problem.Further, anything described in relation to the first embodiment may beequally applicable to the second embodiment and vice versa.

FIG. 1a shows a cross-sectional exploded view of a valve arrangement.The valve arrangement 1 comprises a valve housing 2. The valve housinghas an upper portion at the top of the figure and a lower portion at thebottom of the figure, which are separated in the figure, but when in usethey are mechanically coupled, e.g. by press fit or a threadedengagement. The arrangement further comprises a main valve member 4 anda control valve member 5, inside the control valve member 5 there is apilot valve member 6 (shown in e.g. FIG. 2a ) acting as a pressureregulator. The valve members are biased inside the housing by biasingmeans 14, 19 (shown as springs). The biasing means may be any type ofspring providing a suitable spring force and fitting into the housingspace.

The figure further illustrates the second port 8 in the lower portion ofthe valve housing 2. Moreover, the arrangement comprises the movablemain valve seat member 9, which is further illustrated in the followingfigures, especially FIG. 7b . The valve seat member 9 a comprise anintegrated blocking means comprising blocking portions 91 andintermediate openings 92, as has been explained above. Further, analternative main valve seat member 9 b is illustrated. The alternativemain valve seat member 9 b also comprise an integrated blocking meanscomprising blocking portions 91 and intermediate openings 92. Thedifference is that the blocking portions 91 decrease in size as thedistance from the base of the valve seat member increase.Correspondingly, the intermediate openings 92 in the alternative valveseat member 9 b increase in size as the distance from the base of thevalve seat member increase. Hereby, the blocking means may block themost damping fluid in the lower parts of the stroke, and allow anincreased flow as the strokes increase. Thus, the orifice O_(R3) of R3will increase more than linearly relative the stroke length, as isillustrated in FIG. 6d . Most details in FIG. 1a will be furtherexplained in relation to FIGS. 3a-5a , where their respective functionalso will be described. FIG. 1a is mainly included in the application toclarify the form of each component and thereby facilitate the readingand understanding of the application.

FIG. 1b is a corresponding illustration of the valve arrangement as isshown in FIG. 1a , but wherein the blocking means 10 is a separate unitwhich comprise blocking portions 91 and intermediate openings 92. As hasbeen explained above, these have the same function as the blockingportions 91 and intermediate openings 91 in the first embodiment.Further, FIG. 1b comprise a biasing means 11 for holding the blockingunit 10 in position. In FIG. 1b the biasing unit 11 is illustrated as awave washer, but may be any type of biasing means such as a spring or anelastic material, as long as it provides enough biasing force and can befitted into the housing. Although it is not illustrated in FIG. 1b , itwould be fully possible to adjust the form of the blocking means 10 sothat the blocking portions 91 increase in size as they the distance fromthe base of the blocking means increase. Correspondingly, theintermediate openings 92 decrease in size as the distance from the baseof the blocking means increase. Hereby, the blocking means may block themost damping fluid in the lower parts of the stroke, and allow anincreased flow as the stroke increase. Thus, the orifice O_(R3) of R3will increase more than linearly relative the stroke length.

FIGS. 2a and 3a shows a cross-section of an embodiment of the valvearrangement 1 when the main valve member 4 is in a closed position toblock a main flow (not shown) from the first port 7 to the second port8, wherein FIG. 3a is a close-up cross-section of FIG. 2a . The valvearrangement 1 comprises a valve housing 2, a pilot chamber 3, a mainvalve member 4, and a control valve member 5. The valve housing 2comprises a first and a second port 7, 8. In the illustrated embodiment,the first and second ports act as inlet and outlet ports, respectively,for inlet and outlet of hydraulic fluid. The pilot chamber 3 is definedby the space formed between the upper surface 41 of the main valvemember and inner walls of the valve housing 2. The pilot chamber 3 is influid communication with the first port 7 via a first axial through hole32 in the main valve member 4 and with the second port 8 via a secondaxial through hole 33 in the main valve member 4. There may be severalaxial holes provided in the main valve member for these purposes. Thepilot pressure Pp acting on the upper surface 41 of the main valvemember 4 is defined by a hydraulic pressure in the pilot chamber 3.

The main valve member 4 is axially movably arranged in the valve housing2 and is arranged to interact with the movable main valve seat member 9a in order to restrict or regulate a pressure in a main fluid flow 30(shown in e.g. FIGS. 4a and 5a ) between the first port 7 and the secondport 8 in response to a pilot pressure Pp acting on an upper surface 41of the main valve member 4. In this embodiment, the main valve member 4is held towards the main valve seat member 9 a in a closed position. Themain valve member may be resiliently loaded by any spring members or mayitself be flexible and/or resilient to achieve a desired resilientloading towards the movable main seat valve member 9 a.

The control valve member 5 is of a substantially cylindrical shape andis arranged coaxially with and partially within the main valve member.The control valve member 5 is furthermore movable in an axial directionrelative the main valve member in response to an actuating force actingon the control valve member. In this embodiment, the actuating force isreceived by an actuating rod 35. The actuating rod may be an axiallymovable member on which a solenoid exerts a force in response to anelectric current.

Further, the closed state shown in FIG. 2a may be derived from that thepressure from port 7 and/or 8 has not yet reached a threshold value whenthe main valve member 4 is lifted towards the pilot chamber 3. Thisthreshold value corresponds to when the lifting force generated from thepressure in any one of the first or second port 7, 8 acts on a liftingareas 42, 43 of the main valve member 4 exceed the counter acting forcefrom the pilot pressure Pp in the pilot chamber 3 acting on the uppersurface 41 of the main valve member 4. This is further explained inrelation to FIGS. 4a and 5a where a regulated main flow 30 isillustrated.

As most clearly illustrated in the close-up shown in FIG. 3a , the valvehousing member comprises a circumferential aperture 25, having a radialinner wall 26 and a radial outer wall 27. In connection with the radialinner wall 26 there is another aperture forming a fifth restriction R1′.The fifth restriction R1′ allows the damping fluid to enter thecircumferential aperture 25 so as to pressurize the movable main valvemember 9 in response to a pressure in port 7. The blocking portion 91 isalso illustrated as a solid wall in the cross-section of FIG. 3a .Further, FIG. 3a illustrates a bleed flow 20 flowing between the firstand second ports through an opening in the main valve member 4, into thecontrol valve member 5 and passing along the pilot valve member 6 andthen back through the control valve member 5 and the main valve member4. This bleed flow is a limited flow which is substantially lower flowthan the maximum main fluid flow. The regulated bleed flow 20corresponds to the first stage flow q1 in FIG. 6e , i.e. before thethree curves depart from each other. This will be further elaborated inrelation to FIG. 6 e.

FIGS. 2b and 3b are corresponding to FIGS. 2a and 3a , respectively, butwith the difference that the blocking means 10 is a separate unit whichcomprise blocking portions 91 and intermediate openings 92, as has beenexplained above. Also, the biasing means 11 is illustrated in FIGS. 2band 3b . The biasing member 11 is holding the blocking means 10 againstthe movable valve member 9 b with support from a surface on the mainvalve member 4.

FIGS. 4a and 4b are two close-up illustrations of the two embodiments,wherein the main valve member 4 and main valve seat member 9 a is in apartly open position to allow a regulated main flow 30 from the firstport 7 to the second port 8, i.e. a flow during compression stroke. Asillustrated, the movable main valve seat member 9 and main valve member4 are held together in a position axially displaced relative the valvehousing 2 when compared to the closed position in FIGS. 2a /2 b and 3a/3 b. In this position, a regulated main fluid flow 30 is allowed fromthe first port 7 to the second port 8, and is restricted by the firstrestriction R1 plus the fifth restriction R1′ first (upstream, closestto the first port) and then restricted by the second restriction R2downstream of the first restriction R1. The radial inner wall 26 incooperation with the movable valve seat 9 forms a part of the firstrestriction (R1) and the radial outer wall (27) together with themovable valve seat 9 form a part of the second restriction (R2). In anypartly open state the orifice of the first restriction R1 is smallerthan the orifice of the second restriction R2, since the tworestrictions are formed as circumferential restrictions and beingradially displaced. Since the second restriction has a largercircumference its orifice will always be larger than the orifice of thefirst restriction, when formed with a common delimiter upwards (themovable valve seat member 9) and downwards (the radial side walls of thehousing). Further, the fifth restriction R1′ has a constant opening.Hereby, the sum of the first R1 and fifth R1′ restriction is initiallylarger than the second restriction R2, but as the stroke S increases thesecond restriction becomes larger than the sum of the first and fifthrestriction, this is illustrated in FIGS. 6c and 6 d.

Thus, in FIGS. 4a and 4b a pressure from the damping fluid in port 7causes the opening axial displacement of the main valve member 4 (actingon the lifting areas 42 and 43) and the main valve seat member 9 (actingon the lifting area 21 a as illustrated in FIG. 6b ). The movement is,as earlier explained, dependent on the counteracting pressure from thepilot chamber 3 acting on the main valve member 4. Hereby, a regulatedmain flow of damping fluid is allowed to flow from the first to thesecond port 7, 8. This type of regulation corresponds to the secondstage flow q2 in FIG. 6e , i.e. after the three curves depart from eachother. Since two serial and cooperative restrictions R1 and R2 are usedto regulate the flow, a soft opening when going from the first stage q1to the second stage q2 may be achieved. This will be further elaboratedin relation to FIG. 6e as mentioned before.

FIGS. 5a and 5b are also a close-up of the view in FIG. 2a /2 b, butwhere the main valve member 4 is in a partly open position to allow aregulated main flow 30 from the second port 8 to the first port 7, i.e.a flow during rebound stroke.

When comparing FIG. 5a to FIG. 4a , it is only the movable main valveseat member 9 that has been moved from being arranged tightly againstthe main valve member 4, to instead being arranged tightly against thevalve housing 2. This is achieved through a flow (pressure) of dampingfluid from the second port 8 to the first port 7, which acts on theupper surface, being a lifting area 22, of the movable main valve seatmember 9 and also acts on the lifting area 43 of the main valve member4, but in an opposite direction so that the main valve member 4 and themain valve seat member are separated. The pressure in the second port 8will keep the main valve seat member 9 pressed against the valve housing2 throughout the rebound stroke. Also, depending on the level ofpressure, the opening between the main valve member 4 and the main valveseat member determines both the orifices O_(R3), O_(R4) of thirdrestriction R3 and the fourth restriction R4. The third restriction R3enables the pressure-regulated flow in rebound stroke. Since the twoserial and cooperative restrictions R3 and R4 are used to regulate theflow, a soft opening when going from the first stage q1 to the secondstage q2 may be achieved. The third restriction R3 is partly shieldedalong its outer envelope surface by the blocking portions 91. Hereby,the orifice of R3 is smaller than the orifice of R4 regardless of thestroke length.

As further shown in FIG. 5a , the main valve member 4 comprise a flangeportion for cooperating with the movable valve member to constitute thethird and fourth restrictions R3, R4. The flange part meshes with theblocking portions 91. Further, the main valve member comprises ageometrically defined circumferential aperture 45. The aperture has aradial inner wall 46 and a radial outer wall 47. The radial inner wall46 forms a part of the fourth restriction R4 and the radial outer wall47 forms a part of the third restriction R3, in cooperation with themovable valve member 9. Further, the aperture 46, inner and outer walls46, 47 may all be arranged in the flange portion. Further, the sixthrestriction R3′, is an opening into the aperture 45, which fluidlyconnects the second port 8 to the aperture 47. Thus, the aperture 46,inner wall 46 and outer wall 47, in the main valve member 4 has asimilar function as the aperture 26, inner wall 26 and outer wall 27 inthe housing as explained above, but for achieving a soft opening in therebound flow, in the same way as soft opening is achieved in thecompression flow.

When comparing FIG. 4a and FIG. 5a , the above-mentioned advantage withhaving a movable valve seat member 9 and thereby getting a more flexiblearea pressure ratio between compression pressure area and reboundpressure area may be understood. In the illustrated embodiment the arearatio between the compression area and the rebound area may be adjustedwithout changing the pilot pressure area. In a solution where the mainvalve seat is fixed, the sum of the compression pressured area andrebound pressured area is equal to the pilot pressured area. However,with a movable main valve member, it is possible that the sum is greaterthan the pilot pressured area, since the movable valve seat member ismoved and thereby the compression pressure and rebound pressure acts atdifferent surfaces. This allows forming the valve arrangement togenerate the desired damping forces in both the compression stroke andthe rebound stroke without compromising with one of the forces.

Further, FIGS. 5b and 5c shows two different view of the same embodimentand state of the valve arrangement. FIG. 5b mainly illustrates the mainflow 30 (which is left out of FIG. 5c for clarity reasons). In bothFIGS. 5b and 5c the blocking means is a separate unit, not beingintegrated with the movable valve seat member 9. On the left side theflow through the third R3 and fourth R4 restrictions is illustrated. Onethe right hand side the cross-section is taken through the blockingportion 91 why the flow takes a path on a side of said blocking portion91, and though the sixth restriction R3′, always being open (illustratedby the top dotted path in the right part of the figure.

Moreover, 5 c illustrates the details also shown in FIG. 5a , but in theembodiment with the blocking means being a separate blocking unit 10.Just below the inner wall 46 of the main valve member 4, one opening 92in the blocking unit 10 is illustrated. This correspond to the areaO_(R3) in FIG. 7c , where the main fluid flow may flow when the valve isat least partly opened, i.e. the valve is more than zero.

FIGS. 6a and 6b further illustrates a principle sketch of thepressurized areas of the movable valve seat member 9. In FIG. 6a thepressurized areas 21 b, 21 c and 22 corresponds to the area acting onthe movable valve seat member 9 when the main valve is closed, asillustrated in e.g. FIGS. 2a and 3a . The area 21 b corresponds to theportion of the movable valve seat member protruding from the valvehousing in a radially inwards direction. The area 21 c corresponds tothe portion of the movable valve seat member arranged on top of thecircumferential aperture 25 in the valve housing. That is, this aperturemay be filled with pressurized damping fluid. Further, the area 22corresponds to the portion of the movable valve seat member 9 extendingin a radially outwards direction from the main valve member's radiallyouter corner.

Further, FIG. 6b shows a cross-section of a side portion of the mainvalve seat member where the lifting surface area during regulatedcompression stroke is illustrated. The pressurized area 21 a on themovable valve seat member 9 illustrated is when the main valve member isat least partly opened. The area corresponds to the whole lower surfaceof the movable valve seat member 9.

FIG. 6d shows a graph over the orifice openings O_(R1)+O_(R1′) andO_(R2) as a function of the stroke length S. The first orifice O_(R1)corresponds to the orifice of the first restriction R1. This orificeO_(R1) is also illustrated by the envelope surface of the circle in FIG.6c , and denoted with O_(R1), which is thus dependent on the strokelength S. The stroke length is the axial distance between the movablevalve seat member 9 and the main valve housing 2, when being in aregulated position, see for example in FIG. 3b . The second orificeO_(R2) corresponds to the orifice O_(R2) of the second restriction R2.This orifice is also illustrated by the envelope surface of the circlein FIG. 6c , and denoted with O_(R2). The fifth orifice O_(R1′)corresponds to the orifice of the fifth restriction R1′. This orificeO_(R1′) is also illustrated by a surface in FIG. 6c denoted withO_(R1′), which corresponds to the opening into the circumferentialaperture in the main valve housing 2. As already explained above, FIG.6c shows an illustration of a cross-sectional side-view of the mainvalve seat member where the first O_(R1), second O_(R2) and fifthO_(R1′) orifices are illustrated at a given stroke length S. From thisillustration it is apparent how the first O_(R1) and second O_(R2)orifices vary with the stroke length S, but the fifth O_(R1′) orifice isstatic.

In the initial phase of the regulated compression stroke, i.e. when R1and R2 is just opening from a closed position, the restriction will becarried out in the second restriction, which is shown in FIG. 6d , sincethe orifice of the second restriction R2 is smaller than the orifice ofthe first and fifth restriction R1+R1′, in said initial phase. As soonas the orifice of the second restriction O_(R2) is larger than thecombined orifice of the first and fifth restriction O_(R1)+O_(R1′), therestriction is instead carried out at the first and fifth restrictions.

Further, as the graph in FIG. 6d illustrates, the combined first andfifth orifices O_(R1) and O_(R1′) are larger than the second orificeO_(R2) during the initial stroke, but at one point, the second orificeO_(R2) is larger than the combined first and fifth orifices O_(R1) andO_(R1′), and increases faster during the same stroke length.

The size relationships between the orifices of the differentrestrictions may vary without departing from the inventive concept. Byadjusting the orifice size relationships, the intersecting point between“O_(R1)+O_(R1′)”-curve and the “O_(R2)”-curve the shown in FIG. 6d maybe moved. The orifice size of O_(R1′) is represented by where the“O_(R1)+O_(R1′)”-curve intercepts the Y-axis. The relation between thesize of the first and second restrictions' orifices O_(R1) isillustrated by the different inclinations of the two curves in FIG. 6d .Further, by increasing the relative size of the fifth orifice O_(R1′)relative the maximum orifice size of the first orifice O_(R1) the softopening is prolonged.

There is no illustration of the orifices of R3, R3′ and R4, but theycorrespond to the same principles as disclosed in FIG. 6d . WhereinO_(R3) correspond to O_(R1), O_(R3′) correspond to O_(R1′) and O_(R4)correspond to O_(R2).

There is further a dotted bended line in FIG. 6d , which represents theorifice O_(R3)+O_(R′3) when the alternative blocking means 9 b is used,i.e. wherein the blocking means 9 b blocks the most damping fluid in thelower parts of the stroke, and allow an increased flow as the strokesincrease. The form of the blocking portion 91 will determine the curvingof the O_(R3)+O_(R′3) dashed line, and may be adapted to a desiredcharacter.

The maximum orifice size of the first orifice O_(R1) may be about50%-95% of the maximum orifice size of the second orifice O_(R2). In oneembodiment the maximum orifice size of the first orifice O_(R1) is about70%-90% of the maximum orifice size of the second orifice O_(R2). Inanother embodiment maximum orifice size of the first orifice O_(R1) isabout 75%-85% of the maximum orifice size of the second orifice O_(R2).

The orifice size of the fifth orifice O_(R1′) may be about 0.1%-10% ofthe maximum orifice size of the first orifice O_(R1). In one embodimentthe orifice size of the fifth orifice O_(R1′) is about 0.3%-3% of themaximum orifice size of the first orifice O_(R1). In another embodimentthe orifice size of the fifth orifice O_(R1′) is about 0.5%-1% of themaximum orifice size of the first orifice O_(R1).

Analogy, the maximum orifice size of the third orifice O_(R3) may beabout 50%-95% of the maximum orifice size of the fourth orifice O_(R4).In one embodiment the maximum orifice size of the third orifice O_(R3)is about 70%-90% of the maximum orifice size of the fourth orificeO_(R4). In another embodiment maximum orifice size of the third orificeO_(R3) is about 75%-85% of the maximum orifice size of the fourthorifice O_(R4).

The orifice size of the sixth orifice O_(R3′) may be about 0.1%-10% ofthe maximum orifice size of the third orifice O_(R3). In one embodimentthe orifice size of the sixth orifice O_(R3′) is about 0.3%-3% of themaximum orifice size of the third orifice O_(R3). In another embodimentthe orifice size of the sixth orifice O_(R3′) is about 0.5%-1% of themaximum orifice size of the third orifice O_(R3).

Finally, FIG. 6e shows graph over the pressure P as a function of theflow q in a compression stroke, in three different dampers withdifferent damping characteristics. All functions comprise a common firststage q1, where a regulated bleed flow is illustrated. In the secondstage q2, starting from where the three functions separated from eachother, corresponds to a pressure regulated main fluid flow. The firstdamping character DC1, illustrates a sharp opening, which is the commonbehaviour in 2-way valves today. The second and third functions DC2 andDC3, both illustrate a soft opening, i.e. when the solution described inthis application is used. The difference between the two is the orificesize of the fifth restriction R1′. That is, by altering the size of thefifth restriction's orifice the character of the soft opening may beadjusted. In the second function DC2, the fifth orifice O_(R1′) issmaller than in the third function DC3 which consequently has a largerorifice O_(R1′). The illustrated pressure P as a function of the flow qis also applicable in the rebound stroke. However, then the size of thesixth restriction's orifice O_(R3′) should be adjusted in relation tothe third O_(R3) and fourth O_(R4) restriction orifices in order toadjust the character of the soft opening.

FIG. 7a is an illustration of the main valve seat member 9 a when havingan integrated blocking means. The blocking means consists of blockingportions 91. There may be a plurality of blocking portions 91, in thisspecific example three portions are used, and evenly distributed. Inother embodiments more blocking portions may be used, e.g. 4, 5, 6, 7 or10 or more. Between the blocking portions 91 there are openings 92allowing the damping fluid to flow between the first and second ports.FIG. 7a also comprise the alternative main valve seat member 9 b whenhaving an integrated blocking means, but where the blocking portions 91decrease in size as the distance from the base of the valve seat memberincrease. Correspondingly, the intermediate openings 92 in thealternative valve seat member 9 b increase in size as the distance fromthe base of the valve seat member increase. Hereby, the blocking meansmay block the most damping fluid in the lower parts of the stroke, andallow an increased flow as the strokes increase. This has also beendescribed in relation to FIG. 6 d.

FIG. 7b shows a perspective view (from below) of an alternativeembodiment wherein the main valve seat member and the blocking means arerepresented by separate units. The blocking unit 10 then comprise theblocking portions 91 and intermediate openings 92. There may be aplurality of blocking portions 91 (and consequently openings), in theillustrated example three blocking portions are used, and evenlydistributed. In other embodiments more portions may be used, e.g. 4, 5,6, 7 or 10 or more.

FIG. 7c shows an illustration of the third, fourth and sixth orifices ata given stroke length S. The figure corresponds to FIG. 6c , butrepresents the orifices for the restrictions in the rebound stroke. Theorifice O_(R3) is illustrated by the envelope surface of the lowercircle, but with the without the striped areas 91 corresponding to theblocking portions 91. Thus, the third orifice O_(R3) is dependent on thestroke length S. The stroke length is in the rebound flow, the axialdistance between the movable valve seat member 9 and the main valvemember 4, when being in a regulated position, see for example in FIG. 5a/5 b. The fourth orifice O_(R4) corresponds to the orifice of the fourthrestriction R4. This orifice is illustrated by the envelope surface ofthe top circle, and denoted with O_(R4). The sixth orifice O_(R3′)corresponds to the orifice of the sixth restriction R3′. This orificeO_(R3′) is also illustrated by a surface in FIG. 7c , which correspondsto the opening into the circumferential aperture into the aperture 45.From FIG. 7c it is apparent how the third O_(R3) and fourth O_(R4)orifices cooperatively vary with the stroke length S, but the sixthorifice O_(R3′) is static and stroke independent.

FIG. 7d illustrates the movable valve seat member 9 c when being a shimor washer, from a top view. It is shown that the movable valve seatmember 9 c has an outer diameter D1 and an inner diameter D2.Furthermore, the washer comprises three radial steering projections 93.The steering projections are sized and adapted to mesh with the mainvalve housing 2. Furthermore, the space between the at least threeradial steering projections 93 in the washer forms intermediate ports 94for allowing the main fluid flow 30 passing from the first 7 to thesecond port 8 during the compression stroke. The steering projections 93and intermediate ports 94 in the embodiment are arranged so that not asingle steering projection 93 has an opposing steering projection on theother side of the washer. With other words, a straight line through anyof the projection 93 and the center of the washer will not go through asecond steering 93 projection but instead go through an intermediateport 94. The reason to this design is that jamming of the movable valveseat member 9 may be prevented if it is tilted (i.e. rotated around anaxis being perpendicular to its center axis) since there are no twodirectly opposite projections along the diameter of the washer. It wouldalso be possible to have more radial steering projections, as long asthey are distributed along the circumferential of the movable valve seatmember 9 so as to avoid jamming if it is tilted. Although the steeringprojections are only illustrated in relation to the washer-shaped valveseat member 9 c, the projections could be applied to the otherembodiments of the valve seat member 9 a, 9 b.

Finally, FIG. 8 shows a side cross-sectional illustration of a shockabsorber 100 having a valve arrangement placed therein. Not all thedetails of the shock absorber are shown since it belongs to known art.Instead FIG. 8 is merely an illustration to show in what way the valvearrangement described herein may be implemented in a shock absorber. Theshock absorber comprises a first working chamber 101 and a secondworking chamber 102. Further, the shock absorber 100 comprises a pistonrod 103 attached to the housing of the valve arrangement 1. A sealingmember 104 is arranged to the valve housing and divides the firstworking chamber 101 from the second working chamber 102. The firstworking chamber 101 is fluidly connected to the first port 7 of thevalve arrangement and the second working chamber 102 is fluidlyconnected to the second port 8 of the valve arrangement 1. It should befurther understood that the shock absorber in FIG. 1 also illustrateshow a valve arrangement 1 would be mounted in e.g. a front fork orequivalent damping equipment for a vehicle.

Although exemplary embodiments of the present invention have been shownand described, it will be apparent to the person skilled in the art thata number of changes and modifications, or alterations of the inventionas described herein may be made. Moreover, the different embodimentsdescribed above may be combined in different ways without departing fromthe scope of the inventive concept. Thus, it is to be understood thatthe above description of the invention and the accompanying drawing isto be regarded as a non-limiting example thereof and that the scope ofthe invention is defined in the appended patent claims.

The invention claimed is:
 1. A valve arrangement for a shock absorber,said valve arrangement comprising: a valve housing comprising a firstand a second port; a pilot chamber being in fluid communication withsaid first and/or second port, wherein a pilot pressure is defined by ahydraulic pressure in said pilot chamber; and a main valve member beingaxially movably arranged in said valve housing and being arranged tointeract with a main valve seat member in order to restrict a main fluidflow between said first and second ports in response to said pilotpressure acting on said main valve member; wherein the main valve seatmember is movable between a first compression stroke position and asecond rebound stroke position so that, during the compression stroke,the main fluid flow is restricted at a first restriction comprising anorifice and a cooperating serially arranged second restrictioncomprising an orifice, and, during the rebound stroke, the main fluidflow is restricted at a third restriction comprising an orifice and acooperating serially arranged fourth restriction comprising an orifice;and wherein the orifice of said first restriction is controlled by meansof the axial position of the main valve member relative to the valvehousing.
 2. The valve arrangement according to claim 1, wherein thefirst restriction is arranged upstream relative the second restriction,in view of the compression fluid flow direction and the firstrestriction has a smaller orifice than the second restriction's orificein at least an initial stroke and when being at least partly opened. 3.The valve arrangement according to claim 1, wherein the thirdrestriction is arranged upstream relative the fourth restriction, inview of the rebound fluid flow direction, and wherein the thirdrestriction has a smaller orifice than the fourth restriction's orificein at least an initial stroke and when being at least partly opened. 4.The valve arrangement according to claim 1, comprising a fifthrestriction being arranged in series with the second restriction.
 5. Thevalve arrangement according to claim 4, wherein the fifth restrictionhas a constant orifice being independent of the axial position of themain valve member relative the valve housing.
 6. The valve arrangementaccording to claim 1, comprising a sixth restriction being arranged inseries with the fourth restriction.
 7. The valve arrangement accordingto claim 6, wherein the sixth restriction has a constant orifice beingindependent of the axial position of the main valve member relative thevalve housing.
 8. The valve arrangement according to claim 6, whereinsaid main valve member further comprises a geometrically definedcircumferential aperture having a radial inner wall and a radial outerwall, wherein the radial inner wall forms a part of the fourthrestriction and the radial outer wall forms a part of the thirdrestriction, and wherein said sixth restriction is at least one openinginto said circumferential aperture in said main valve member.
 9. Thevalve arrangement according to claim 1, wherein said main valve memberfurther comprises a geometrically defined circumferential aperturehaving a radial inner wall and a radial outer wall, wherein the radialinner wall forms a part of the fourth restriction and the radial outerwall forms a part of the third restriction.
 10. The valve arrangementaccording to claim 1, wherein the orifice of the third restriction is acircumferential orifice, the valve arrangement further comprising ageometrically defined circumferential blocking means for blocking atleast a part of the circumferential orifice of the third restriction, sothat the third restriction has a smaller orifice than the fourthrestriction's orifice in at least an initial stroke and being at leastpartly opened.
 11. The valve arrangement according to claim 10, whereinsaid blocking means is an axially extending wall blocking an envelopeouter surface of said radial outer wall.
 12. The valve arrangementaccording to claim 10, wherein said blocking means forms an integralpart of the valve seat member.
 13. The valve arrangement according toclaim 10, wherein said blocking means constitute a separate blockingmember.
 14. The valve arrangement according to claim 1, wherein at leastone of the orifices of said second restriction, third restriction and/orfourth restriction is controlled by means of the axial position of themain valve member relative the valve housing.
 15. A shock absorbingdevice for a vehicle suspension comprising: at least one workingchamber, and a valve arrangement according to claim 1, for controllingthe flow of a damping medium fluid to/from said at least one workingchamber to control the damping characteristics of said shock absorbingdevice.
 16. A valve arrangement for a shock absorber, said valvearrangement comprising: a valve housing comprising a first and a secondport; a pilot chamber being in fluid communication with said firstand/or second port, wherein a pilot pressure is defined by a hydraulicpressure in said pilot chamber; a main valve member being axiallymovably arranged in said valve housing and being arranged to interactwith a main valve seat member in order to restrict a main fluid flowbetween said first and second ports in response to said pilot pressureacting on said main valve member; wherein the main valve seat member ismovable between a first compression stroke position and a second reboundstroke position so that, during the compression stroke, the main fluidflow is restricted at a first restriction and a cooperating seriallyarranged second restriction, and, during the rebound stroke, the mainfluid flow is restricted at a third restriction and a cooperatingserially arranged fourth restriction, wherein said main valve memberfurther comprises a geometrically defined circumferential aperturehaving a radial inner wall and a radial outer wall, wherein the radialinner wall forms a part of the fourth restriction and the radial outerwall forms a part of the third restriction.